The Woodlouse is very unique in its choice of habitat in comparison to the rest of its class, Crustacean. Crustaceans are predominantly aquatic, of the some 38,000 species known, 84% live in the sea, 13% live in freshwater and only 3% are terrestrial.
The Woodlouse has had to overcome many problems to enable it to inhabit the terrestrial world, water-balance, temperature tolerance, respiration, reproduction and digestion to mention but a few. Woodlice are members of the order Isopoda; Isopoda comes from the Greek isos meaning'equal' and podes meaning'feet'. Most of the later Isopoda have favoured walking rather than swimming and evolved seven pairs of thoracic limbs, which are complimentary to the life of a bottom dwelling walking organism rather than a swimming one. The way in which woodlice probably made the leap from aquatic to terrestrial life was in stages; habitats allowing semi-terrestrial existence were probably crucial. The fact that terrestrial crustaceans have body fluids with high osmotic pressure would suggest that these crucial semi-terrestrial habitats were perhaps salt marshes or mangrove swamps.
The two key features Isopoda developed to enable them to survive on land was the dorsoventrally flattened body,
which gave extreme stability and the'squat' posture when
walking. The second was the fluid filled brood pouch, which provided the young with a water stable environment to grow up in, to prevent drying out.
Today woodlice have been very successful and have now managed to colonise some of the most extreme environments on earth including deserts in Israel and hypersaline pools in Australia via their fully terrestrial forms.
Woodlice like all Arthropoda are segmented; there are three sections – head, pereon (thorax) and pleon (abdomen) with the tail end called the uropod, as seen in figure 1 below.
Woodlice are dorsoventrally flattened with seven pairs of walking…

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